Added a spherical course & dist given two points routine.
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@ -30,6 +30,8 @@
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#endif
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#include <math.h>
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#include <simgear/constants.h>
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#include <simgear/math/point3d.hxx>
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@ -66,7 +68,8 @@ inline Point3D fgCartToPolar3d(const Point3D& cp) {
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// distance. NOTE: starting point is specifed in radians, distance is
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// specified in meters (and converted internally to radians)
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// ... assumes a spherical world
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inline Point3D calc_lon_lat( const Point3D& orig, double course, double dist ) {
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inline Point3D calc_gc_lon_lat( const Point3D& orig, double course,
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double dist ) {
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Point3D result;
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// lat=asin(sin(lat1)*cos(d)+cos(lat1)*sin(d)*cos(tc))
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@ -96,6 +99,60 @@ inline Point3D calc_lon_lat( const Point3D& orig, double course, double dist ) {
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}
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// calc course/dist
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inline void calc_gc_course_dist( const Point3D& start, const Point3D& dest,
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double *course, double *dist ) {
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// d = 2*asin(sqrt((sin((lat1-lat2)/2))^2 +
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// cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2))
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double tmp1 = sin( (start.y() - dest.y()) / 2 );
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double tmp2 = sin( (start.x() - dest.x()) / 2 );
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double d = 2.0 * asin( sqrt( tmp1 * tmp1 +
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cos(start.y()) * cos(dest.y()) * tmp2 * tmp2));
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// We obtain the initial course, tc1, (at point 1) from point 1 to
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// point 2 by the following. The formula fails if the initial
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// point is a pole. We can special case this with:
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//
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// IF (cos(lat1) < EPS) // EPS a small number ~ machine precision
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// IF (lat1 > 0)
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// tc1= pi // starting from N pole
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// ELSE
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// tc1= 0 // starting from S pole
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// ENDIF
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// ENDIF
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//
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// For starting points other than the poles:
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//
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// IF sin(lon2-lon1)<0
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// tc1=acos((sin(lat2)-sin(lat1)*cos(d))/(sin(d)*cos(lat1)))
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// ELSE
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// tc1=2*pi-acos((sin(lat2)-sin(lat1)*cos(d))/(sin(d)*cos(lat1)))
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// ENDIF
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double tc1;
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if ( cos(start.y()) < FG_EPSILON ) {
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// EPS a small number ~ machine precision
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if ( start.y() > 0 ) {
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tc1 = FG_PI; // starting from N pole
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} else {
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tc1 = 0; // starting from S pole
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}
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}
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// For starting points other than the poles:
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double tmp3 = sin(d)*cos(start.y());
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double tmp4 = sin(dest.y())-sin(start.y())*cos(d);
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double tmp5 = acos(tmp4/tmp3);
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if ( sin( dest.x() - start.x() ) < 0 ) {
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tc1 = tmp5;
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} else {
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tc1 = 2 * FG_PI - tmp5;
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}
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*course = tc1;
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*dist = d * RAD_TO_NM * NM_TO_METER;
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}
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#endif // _POLAR_HXX
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